Computational Investigation of Scrap Charging to the Blast Furnace

This paper examines the idea of using shredded scrap steel as a blast furnace burden material. Charging scrap, or metallics, with the burden offers several possible benefits including increased productivity and decreased fuel rate. In this paper, scrap charging is investigated numerically using a previously presented mathematical model. Furnace operations at both fixed hot metal temperature and fixed top gas temperature are investigated with scrap charged either near the axis, radially uniformly or near the wall. When the average temperature of metal entering the hearth is kept constant, the production and fuel rate are predicted to increase and decrease respectively as scrap feed rate increases. These changes are due to scrap being already fully reduced, thus not requiring heat or carbon for reduction. However, the top gas temperature decreases, particularly when scrap was charged only over the inner half radius of the furnace. Under conditions of constant top gas temperature the productivity and fuel rate still increase and decrease respectively with increasing scrap: ore ratio. Of the three scrap charging patterns tested, the optimum pattern is to charge scrap over the outer half radius of the furnace, which results in the least change in the furnace internal state compared to operations without scrap while showing significant increases in production and decreases in fuel rate. Finally, scrap diameter is found to have only a small effect on the furnace state.